Method, device and system for detecting radio frequency interference

ABSTRACT

A method for detecting radio frequency interference (RFI) is provided. The method includes the following steps. Parameters of at least two pairs of digital subscriber lines (DSLs) are acquired. Sub-carriers having RFI in each pair of the at least two pairs of DSLs are detected according to the parameters. The number of line pairs having RFI on the same sub-carrier in the DSLs is counted, and if the number of the line pairs occurring RFI on the sub-carrier is greater than a preset threshold, or if a ratio of the number of the line pairs occurring RFI on the sub-carrier to a line pair number of the at least two pairs of DSLs is greater than a preset threshold, it is determined that RFI exists at a frequency corresponding to the sub-carrier. A device and a system for detecting RFI are further provided. Therefore, RFI frequency existing in xDSL can be detected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2009/071113, filed on Mar. 31, 2009, which claims priority toChinese Patent Application No. 200810142579.X, filed on Jul. 28, 2008,both of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to the filed of communication technology,and more particularly to a method, device and system for detecting radiofrequency interference (RFI).

BACKGROUND

Digital subscriber line (DSL) technology is a high speed transmissiontechnology for data transmission over telephone twist pair, that is,unshielded twist pair (UTP). The DSL technology includes asymmetricaldigital subscriber line (ADSL), very-high-bit-rate digital subscriberline (VDSL), single-pair high-bit-rate digital subscriber line (SHDSL),asymmetrical digital subscriber line 2 (ADSL2), asymmetrical digitalsubscriber line 2plus (ADSL2plus), and very-high-bit-rate digitalsubscriber line 2 (VDSL2), with xDSL being a general designation for theabove DSL technology.

Within the frequency range used by an xDSL, a wide range of radiofrequency waves exist, these waves may be used in a broadcastingstation, for radio communication, and the like. Radio frequency bands inChina are specified as follows: 120-300 kHz is used for long-waveamplitude modulation broadcast; 525-1605 kHz is used for medium-waveamplitude modulation broadcast; and 3.5-29.7 MHz is used for short-waveamplitude modulation broadcast, single sideband communication, andamateur radio.

All the frequencies used by the radio services overlap more or less withthe frequencies used by xDSL services. When radio waves transmitted bythe radio services are coupled to an xDSL, and have the same frequencyas that of some of sub-carriers of the xDSL, the transmission of thexDSL sub-carriers are affected, which causes instability of the xDSLservices and generates an error or disconnection. Such radiointerference is referred to as RFI.

RFI band specified by ITU-T is a measure for shielding RFI proposed byADSL2plus and VDSL2. If the band range of RFI interference is known, theDSL sub-carriers at these frequency bands may be shielded. In thismanner, RFI interference at these frequencies will not cause an error ina DSL line, or will not affect the stability of the DSL line. Inaddition, a DSL transceiver may also reduce transmission power at theseRFI frequencies, thus avoiding the interference of the DSL services tobroadcasting services.

Such technologies as RFI band only provide a method for solving RFI whenthe RFI frequency is known. But how to obtain the RFI frequency is notmentioned. Generally, the RFI frequency can only be acquired throughoperator's experience or through investigation. The method does not workif the RFI frequency is not known.

SUMMARY

The embodiments of the present invention provide a method, a device anda system for detecting RFI, which can detect RFI frequency in an xDSL.

In an embodiment, the present invention provides a method for detectingRFI. The method includes the following steps:

Parameters of at least two pairs of DSLs are acquired.

Sub-carriers having RFI in each pair of the at least two pairs of DSLsare detected according to the parameters.

The number of line pairs having RFI on the same sub-carrier in the DSLsis counted, if the number of the line pairs having RFI on thesub-carrier is greater than a preset threshold, or if a ratio of thenumber of the line pairs having RFI on the sub-carrier to the number ofline pairs of the at least two pairs of DSLs is greater than a presetthreshold, it is determined that the RFI exists at a frequencycorresponding to the sub-carrier.

In an embodiment, the present invention further provides a detectingdevice. The detecting device includes an acquiring unit, a detectingunit, a counting unit, and a determining unit.

The acquiring unit is configured to acquire parameters of at least twopairs of DSLs. The detecting unit is configured to detect sub-carriershaving RFI in each pair of the at least two pairs of DSLs according tothe parameters. The counting unit is configured to count the number ofline pairs having RFI on the same sub-carrier in the DSLs. Thedetermining unit is configured to determine whether the number of linepairs counted by the counting unit is greater than a preset threshold,or whether a ratio of the number of line pairs counted by the countingunit to the number of line pairs of the at least two pairs of DSLs isgreater than a preset threshold, and if so, the detecting unitdetermines that the RFI exists at a frequency corresponding to thesub-carrier.

In an embodiment, the present invention further provides a DSL system,which includes a first device and a second device. The first deviceincludes an acquiring unit, a detecting unit, a counting unit, and adetermining unit.

The acquiring unit is configured to acquire parameters of at least twopairs of DSLs from the second device. The detecting unit is configuredto detect sub-carriers having RFI in each pair of the at least two pairsof DSLs according to the parameters. The counting unit is configured tocount the number of line pairs having RFI on the same sub-carrier in theDSLs. The determining unit is configured to determined whether thenumber of line pairs counted by the counting unit is greater than apreset threshold, or whether a ratio of the number of line pairs countedby the counting unit to the number of line pairs of the at least twopairs of DSLs is greater than a preset threshold, and if so, thedetecting unit determines that the RFI exists at a frequencycorresponding to the sub-carrier.

With the method, device and system for detecting RFI provided in theembodiments of the present invention, the RFI frequency existing in anxDSL can be detected, thus solving the problem of RFI. Therefore, theproblem in the prior art that the RFI existing in the xDSL cannot besolved if the RFI frequency is not known in advance, is solved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for detecting RFI according to anembodiment of the present invention;

FIG. 2 is an effect drawing of detecting RFI by utilizing the methodaccording to the embodiment of the present invention;

FIG. 3 is a structural view of a device for detecting RFI according toan embodiment of the present invention; and

FIG. 4 is a diagram showing a DSL system according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

The present invention provides a method, a device and a system fordetecting RFI, which can detect RFI frequency existing in an xDSL.

As shown in FIG. 1, in an embodiment, the present invention provides amethod for detecting RFI. The method includes the following steps:

Step S100: Acquire parameters of at least two pairs of DSLs.

Step S102: Detect sub-carriers having RFI in each pair of the at leasttwo pairs of DSLs according to the parameters.

Step S104: Count the number of line pairs having RFI on the samesub-carrier in the DSLs. If the number of the line pairs having RFI onthe sub-carrier is greater than a preset threshold, or if a ratio of thenumber of the line pairs having RFI on the sub-carrier to the number ofline pairs of the at least two pairs of DSLs is greater than a presetthreshold, it is determined that RFI exists at a frequency correspondingto the sub-carrier.

The signal-to-noise ratio of a certain sub-carrier of an xDSL isSNR_(i)=PSD_(Trans)+H log_(i)−PSD_(Noise), in which, SNR_(i) is thesignal-to-noise ratio of the sub-carrier, PSD_(Trans) is the logarithmvalue of a transmit power spectral density of an xDSL transmitting endon this carrier, H log_(i) is the logarithm value of a twisted pairtransfer function, and PSD_(Noise) is the logarithm value of a noisepower spectral density of a receiving end. When the RFI is coupled to anxDSL line, the energy of the RFI is received by an xDSL receiving end,such that the noise power spectral density PSD_(Noise) received by thesub-carrier within the RFI band is increased, thus reducing thesignal-to-noise ratio.

Each sub-carrier of the xDSL independently bears data. The bit numbertransported by a certain sub-carrier during one transmission period iscalculated according to the following Shannon's formula:B _(i)=(SNR_(i)−SNRM arg in_(i)+CodingGain−SNRGap)/(3db/bit)

B_(i) is the bit number transmitted by this sub-carrier during onesignal period, SNRM arg in_(i) is a signal-to-noise ratio margin,CodingGain is the gain caused by coding, and SNRGap is the gap betweenxDSL bearer and theoretical Shannon's formula. Therefore, if thesignal-to-noise ratio of a certain sub-carrier in the xDSL line isreduced, B_(i) of the sub-carrier may thus be decreased indirectly.

Therefore, if RFI is coupled to the line, the three features ofsub-carriers within the RFI band range appear: PSD_(Noise) increases,SNR_(i) decreases, and B_(i) decreases. But the PSD_(Noise), SNR_(i) andB_(i) of surrounding sub-carriers are not affected. Whether RFI existsin an xDSL line can be detected through one of the three features. Allthe parameters of PSD_(Noise), SNR_(i) and B_(i) can be acquired on anxDSL transceiver.

In another embodiment of the present invention, in the step S100, theparameters include PSD_(Noise), SNR_(i) or B_(i). Generally, theparameters of at least two pairs of DSLs within a range, for example, aregion, are collected.

In step S102, sub-carriers having RFI in each pair of the at least twopairs of DSLs are detected according to the parameters, which can bespecifically implemented through the following methods.

1. In the case that the parameter is B_(i), i is the sub-carriersequence number on each pair of the at least two pairs of DSLs, that is,i=1, 2, . . . , m:

If the B_(i) for the sub-carrier is less than a maximum value of theB_(i) of more than three adjacent sub-carriers on its left side by 2bits (or more), and is less than a maximum value of the B_(i) of morethan three adjacent sub-carriers on its right side by 2 bits (or more),it indicates that the i^(th) sub-carrier of the line pair suffers RFI.For example, 5 sub-carriers exist on both the left side and the rightside of the i^(th) sub-carrier, if B_(i)≦max(B_(i−1), B_(i−2), B_(i−3),B_(i−4), B_(i−5))−2 and B_(i)≦max(B_(i+1), B_(i+2), B_(i+3), B_(i+4),B_(i+5))−2, it indicates that the i^(th) sub-carrier of the line pairsuffers RFI.

The above sub-carrier i may be a first sub-carrier.

Optionally, when the parameter is B_(i), after the sub-carriers havingRFI in each pair of the at least two pairs of DSLs are detectedaccording to the parameters, the method further includes a step ofdetecting a pilot tone among the sub-carriers having RFI according tothe bit number.

Generally, all pilot tones of a DSL satisfy B_(i)≦max(B_(i−1), B_(i−2),B_(i−3), B_(i−4), B_(i−5))−2 and B_(i)≦max(B_(i+1), B_(i+2), B_(i+3),B_(i+4), B_(i+5))−2, but this is not caused by RFI. Therefore, the pilottone can be excluded from the detected RFI tones according to thecharacteristics of the pilot tone.

For example, if an activation mode of a DSL is ADSL Annex A, and ifB_(i)=0, and i=64, it can be determined that the i^(th) tone is a pilottone, rather than being affected by RFI.

If the activation mode of the DSL is ADSL Annex B, and if B_(i)=0, andi=96, it can be determined that the i^(th) tone is a pilot tone, ratherthan being affected by RFI.

If the activation mode of the DSL is ADSL2, and if B_(i)=2, andB_(i−1)>max(B_(k), k=1, 2, . . . , m)−3, and B_(i+1)>max(B_(k), k=1, 2,. . . , m)−3, it can be determined that the i^(th) tone is a pilot tone,rather than being affected by RFI.

2. In the case that the parameter is SNR_(i), i is the sub-carriersequence number on each pair of the at least two pairs of DSLs, for anyi=1, 2, . . . , m:

If SNR_(i) for the sub-carrier is less than a maximum value of SNR_(i)of more than three adjacent sub-carriers on its left side by 6 dB (ormore), and is less than a maximum value of SNR_(i) of more than threeadjacent sub-carriers on its right side by 6 dB (or more), it indicatesthat the i^(th) sub-carrier of the line pair suffers RFI. For example,if the SNR_(i) of the sub-carrier is less than a maximum value ofSNR_(i) of five adjacent sub-carriers on its left side by 6 dB (ormore), and is less than a maximum value of SNR_(i) of five adjacentsub-carriers on its right side by 6 dB (or more) that is,SNR_(i)≦max(SNR_(i−1), SNR_(i−2), SNR_(i−3), SNR_(i−4) SNR_(i−5))−6, andSNR_(i)≦max(SNR_(i+1), SNR_(i+2), SNR_(i+3), SNR_(i+4), SNR_(i+5))−6, itindicates that the i^(th) sub-carrier of the line pair suffers RFI.

The above sub-carrier i may be a second sub-carrier.

In addition, the parameter of PSD_(Noise) can also be approximated byquiet line noise (QLN) power spectral density. The QLN is measured by anxDSL receiving end during line diagnose or line initialization.

3. In the case that the parameter is PSD_(Noise), i is the sub-carriersequence number on each pair of the at least two pairs of DSLs, for anyi=1, 2, . . . , m:

If PSD_(Noise) for the sub-carrier is less than a maximum value ofPSD_(Noise) of more than three adjacent sub-carriers on its left side by6 dBm/Hz (or more), and is less than a maximum value of PSD_(Noise) ofmore than three adjacent sub-carriers on its right side by 6 dBm/Hz (ormore), it indicates that the i^(th) sub-carrier of the line pair suffersRFI. For example, if the PSD_(Noise) of the sub-carrier is less than themaximum value of PSD_(Noise) of five adjacent sub-carriers on its leftside by 6 dBm/Hz (or more), and is less than the maximum value ofPSD_(Noise) of five adjacent sub-carriers on its right side by 6 dBm/Hz(or more), that is, PSD_(Noise) _(—) _(i)≧max(PSD_(Noise) _(—) _(i−1),PSD_(Noise) _(—) _(i−2), PSD_(Noise) _(—) _(i−3), PSD_(Noise) _(—)_(i−4), PSD_(Noise) _(—) _(i−5))−6 and PSD_(Noise) _(—) _(i)≧max(PSD_(Noise) _(—) _(i+1), PSD_(Noise) _(—) _(i+2), PSD_(Noise) _(—)_(i+3), PSD_(Noise) _(—) _(i+4), PSD_(Noise) _(—) _(i+5))−6, itindicates that the i^(th) sub-carrier of the line pair suffers RFI.

The above sub-carrier i may be a third sub-carrier.

In step S104, if the number of line pairs is used as the presetthreshold, the preset threshold is generally taken as more than 20% ofthe total number of line pairs selected in S100, or about 20%; and if aratio is used as the preset threshold, the preset threshold is generallygreater than 0.2 and less than 1.

In step S104, specifically, the counting the number of line pairs havingRFI on the same sub-carrier in the DSLs may be exemplified as follows.If it is detected that the i^(th) sub-carrier (or, sub-carrier i) of thej^(th) line pair suffers RFI, RFIDetected[i][j]=1 is recorded;otherwise, RFIDetected[i][j]=0 is recorded. In this manner, a 2-D arrayRFIDetected[m][n] of m*n is obtained, in which m is the number ofsub-carriers included in an xDSL, and n is the counted number of linepairs. The count of all line pairs having RFI on each sub-carrier (i.e.,the times of the sub-carriers having RFI) is counted, that is, each rowof the RFIDetected[i][j] is summed to obtain an array RFICount[m] of alength of m, the i^(th) value in this array represents the times of thei^(th) sub-carrier having RFI, that is, the number of the line pairshaving RFI on the i^(th) sub-carrier.

In this method embodiment, RFI is detected through collecting theparameters of at least two pairs of DSLs, the result of which is morecomprehensive than the case that the RFI is detected by adopting one DSLpair.

In this method embodiment, after the frequency corresponding to thesub-carrier having RFI (that is, RFI frequency) is obtained, partial orall sub-carriers of the xDSL at the frequency corresponding to thesub-carrier having RFI can further be closed, so as to avoid the RFIsuffered by the xDSL services. In this manner, RFI at these frequenciesmay not cause error in a DSL line, and may not affect the stability ofthe DSL line. In addition, a DSL transceiver may also reducetransmission power of the RFI frequencies, thus avoiding theinterference of the DSL services to broadcasting services. For example,sub-carrier masking is used to close some xDSL sub-carriers for notbeing used and not bearing data. In this manner, RFI will not affect thexDSL services. In addition, a DSL transceiver may also reducetransmission power of the RFI frequencies, thus avoiding theinterference of the DSL services to broadcasting services.

Specific examples are taken below to illustrate the method described inthe embodiments of the present invention. The parameter of B_(i) for 45ADSL pairs are collected in a certain region in Xi'an, and RFI isdetected by utilizing the method provided in the embodiments of thepresent invention, the result is as shown in FIG. 2. All together, fivefrequency bands exist at which the ratio of the number of line pairshaving RFI to the detected ADSL number of line pairs is greater than40%, and the sequence numbers of the sub-carriers where their peakslocate are 125, 140, 161, 173 and 209 respectively. By multiplying thesub-carrier sequence number with a sub-carrier frequency interval, forexample, 4.3125 kHz, the frequencies corresponding to the fivesub-carriers can be obtained, which are 539 kHz, 604 kHz, 694 kHz, 746kHz and 901 kHz respectively. The broadcasting stations in Xi'ancorresponding to the five frequencies are respectively voice of China,540 KHz; Shanxi cities, 603 KHz; Shanxi news, 693 KHz; Shanxi dramas,747 KHz; and Shanxi countries, 900 KHz.

It can be seen that, the RFI frequencies detected by utilizing themethod provided in the embodiments of the present invention perfectlycoincide with broadcasting stations' actual RFI transmit power. Inaddition, the RFI count diagram also reflects the effect of RFI on thefrequencies corresponding to various sub-carriers. In FIG. 2, among thefive frequencies having RFI, the count corresponding to 694 KHz is thelargest, which represents that the number of line pairs having RFI atthe frequency band is the largest, that is, users having RFI are themost. Moreover, the number of the sub-carriers affected by the RFI isalso the largest, which represents that the frequency band for thisbroadcasting station affected by RFI is the broadest.

As shown in FIG. 3, in an embodiment, the present invention furtherprovides a detecting device. The device includes an acquiring unit 30, adetecting unit 32, a counting unit 34, and a determining unit 36.

The acquiring unit 30 is configured to acquire parameters of at leasttwo pairs of DSLs. The detecting unit 32 is configured to detectsub-carriers having RFI in each pair of the at least two pairs of DSLsaccording to the parameters. The counting unit 34 is configured to countthe number of line pairs having RFI on the same sub-carrier in the DSLs.The determining unit 36 is configured to determined whether the numberof line pairs counted by the counting unit 34 is greater than a presetthreshold, or whether a ratio of the number of line pairs counted by thecounting unit 34 to the number of line pairs of the at least two pairsof DSLs is greater than a preset threshold, and if so, the detectingunit determines that RFI exists at a frequency corresponding to thesub-carrier.

Optionally, the detecting device further includes a configuring unit 37,configured to, according to the frequency corresponding to thesub-carrier having RFI (that is, the RFI frequency) obtained by thedetermining unit 36, close partial or all sub-carriers of an xDSL at theRFI frequency. In this manner, the RFI suffered by xDSL services isavoided.

Optionally, the detecting device further includes a displaying unit 38,which is connected with the counting unit 34, and configured to displaythe number of line pairs having RFI on the same sub-carrier. In thismanner, users or operators can be enabled to visually see the frequencybands having RFI, and which RFIs affect more seriously.

Optionally, the detecting unit 32 may further include a first detectingunit 320, and/or a second detecting unit 322, and/or a third detectingunit 324.

The first detecting unit 320 is configured to detect that a firstsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a bit number of the first sub-carrier is lessthan a maximum bit number among the bit numbers of more than threeadjacent sub-carriers on its left side by 2 bits or more, and is lessthan a maximum bit number among the bit numbers of more than threeadjacent sub-carriers on its right side by 2 bits or more when theparameter is the bit number of a line pair.

The second detecting unit 322 is configured to detect that a secondsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a signal-to-noise ratio of the secondsub-carrier is less than a maximum ratio among the signal-to-noiseratios of more than three adjacent sub-carriers on its left side by 6 dBor more, and is less than a maximum ratio among the signal-to-noiseratios of more than three adjacent sub-carriers on its right side by 6dB or more when the parameter is the signal-to-noise ratio of the linepair.

The third detecting unit 324 is configured to detect that a thirdsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a noise power spectral density of the thirdsub-carrier is less than a maximum density among the noise powerspectral densities of more than three adjacent sub-carriers on its leftside by 6 dBm/Hz or more, and is less than a maximum density among thenoise power spectral densities of more than three adjacent sub-carrierson its right side by 6 dBm/Hz or more when the parameter is the noisepower spectral density of the line pair.

If the detecting unit 32 includes the first detecting unit 320,optionally, the detecting unit may further include a fourth detectingunit 326. The fourth detecting unit 326 is configured to detect a pilottone from the sub-carriers having RFI detected by the first detectingunit 320 according to the bit number of the line pair. Specifically, ifa sub-carrier is a pilot tone, the sub-carrier is not the sub-carrierhaving RFI.

As shown in FIG. 4, in an embodiment, the present invention furtherprovides a DSL system. The system includes a first device 40 and asecond device 42.

The first device 40 includes an acquiring unit 401, a detecting unit403, a counting unit 405, and a determining unit 407. The acquiring unit401 is configured to acquire parameters of at least two pairs of DSLsfrom the second device. The detecting unit 403 is configured to detectsub-carriers having RFI in each pair of the at least two pairs of DSLsaccording to the parameters. The counting unit 405 is configured tocount the number of line pairs having RFI on the same sub-carrier in theDSLs. The determining unit 407 is configured to determined whether thenumber of line pairs counted by the counting unit 405 is greater than apreset threshold, or whether a ratio of the number of line pairs countedby the counting unit to the number of line pairs of the at least twopairs of DSLs is greater than a preset threshold, and if so, thedetecting unit determines that RFI exists at a frequency correspondingto the sub-carrier.

Optionally, the detecting device further includes a displaying unit 409,which is connected with the counting unit 405, and configured to displaythe number of line pairs having RFI on the same sub-carrier. In thismanner, users or operators can be enabled to visually see the frequencybands existing RFI, and which RFIs affect more seriously. Optionally, ifthe detecting device includes the displaying unit 409, it may notinclude the determining unit 407.

Optionally, the detecting unit 403 may further include a first detectingunit, and/or a second detecting unit, and/or a third detecting unit.

The first detecting unit is configured to detect that a firstsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a bit number of the first sub-carrier is lessthan a maximum bit number among the bit numbers of more than threeadjacent sub-carriers on its left side by 2 bits or more, and is lessthan a maximum bit number among the bit numbers of more than threeadjacent sub-carriers on its right side by 2 bits or more when theparameter is the bit number of a line pair.

The second detecting unit is configured to detect that a secondsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a signal-to-noise ratio of the secondsub-carrier is less than a maximum ratio among the signal-to-noiseratios of more than three adjacent sub-carriers on its left side by 6 dBor more, and is less than a maximum ratio among the signal-to-noiseratios of more than three adjacent sub-carriers on its right side by 6dB or more when the parameter is the signal-to-noise ratio of the linepair.

The third detecting unit is configured to detect that a thirdsub-carrier of each pair of the at least two pairs of DSLs is thesub-carrier having RFI if a noise power spectral density of the thirdsub-carrier is less than a maximum density among the noise powerspectral densities of more than three adjacent sub-carriers on its leftside by 6 dBm/Hz or more, and is less than a maximum density among thenoise power spectral densities of more than three adjacent sub-carrierson its right side by 6 dBm/Hz or more when the parameter is the noisepower spectral density of the line pair.

Optionally, the first device may further includes a configuring unit411, which is configured to decide to close partial or all sub-carriersof an xDSL at a frequency corresponding to the sub-carriers having RFI(that is, the RFI frequency) obtained from the determining unit 407according to the RFI frequency, and transmit information of the partialor all sub-carriers to the second device. The information includes, butnot limited to, the sequence numbers of the sub-carriers. The seconddevice is configured to close the partial or all sub-carriers accordingto the information of the partial or all sub-carriers transmitted by thefirst device. In this manner, the RFI suffered by xDSL services isavoided.

In the DSL system provided in the embodiments of the present invention,the first device may be a line management system, and the second devicemay be a DSL access multiplexer (DSLAM). The line management system canacquire the parameters of the at least two pairs of DSLs from the DSLAMthrough simple network management protocol (SNMP) or file transferprotocol (FTP).

The line management system can also acquire the parameters of the atleast two pairs of DSLs from the DSLAM through a network managementsystem. The network management system may interact with the DSLAM andmanage the DSLAM through a Q interface by utilizing SNMP.

Person having ordinary skill in the art may understand that all or partof the steps of the method according to the embodiments of the presentinvention may be implemented by a program instructing relevant hardware.The program may be stored in a computer readable storage medium.

The storage medium may be a Read-Only Memory (ROM), a magnetic disk, ora Compact Disk Read-Only Memory (CD-ROM).

It should be noted that the above embodiments are merely provided forelaborating the technical solutions of the present invention, but notintended to limit the present invention. Although the present inventionhas been described in detail with reference to the foregoingembodiments, it is apparent that person having ordinary skill in the artcan make various modifications or equivalent replacements to thetechnical solutions of the invention without departing from the spiritand scope of the invention. Any modification, equivalent replacement, orimprovement made without departing from the spirit and principle of thepresent invention should fall within the scope of the present invention.

1. A method for detecting radio frequency interference (RFI), the method comprising: acquiring parameters of at least two pairs of digital subscriber lines (DSLs); detecting sub-carriers having RFI in each pair of the at least two pairs of DSLs according to the parameters; and counting the number of line pairs having RFI on the same sub-carrier in the DSLs, wherein if the number of the line pairs having RFI on the sub-carrier is greater than a preset threshold, or if a ratio of the number of the line pairs having RFI on the sub-carrier to the number of line pairs of the at least two pairs of DSLs is greater than a preset threshold, it is determined that RFI exists at a frequency corresponding to the sub-carrier.
 2. The method for detecting RFI according to claim 1, wherein if the parameter is a bit number, the detecting the sub-carriers having RFI in each pair of the at least two pairs of DSLs according to the parameters specifically comprises: detecting that a first sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI, if the bit number of the first sub-carrier is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its left side by 2 bits or more, and is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its right side by 2 bits or more.
 3. The method for detecting RFI according to claim 1, wherein if the parameter is the bit number, after the detecting the sub-carriers having RFI in each pair of the at least two pairs of DSLs according to the parameters, the method further comprises: detecting a pilot tone among the sub-carriers having RFI according to the bit numbers.
 4. The method for detecting RFI according to claim 1, wherein if the parameter is a signal-to-noise ratio, the detecting the sub-carrier having RFI in each pair of the at least two pairs of DSLs according to the parameters specifically comprises: detecting that a second sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI, if the signal-to-noise ratio of the second sub-carrier is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its left side by 6 dB or more, and is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its right side by 6 dB or more.
 5. The method for detecting RFI according to claim 1, wherein if the parameter is a noise power spectral density, the detecting the sub-carrier having RFI in each pair of the at least two pairs of DSLs according to the parameters specifically comprises: detecting that a third sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI, if the noise power spectral density of the third sub-carrier is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its left side by 6 dBm/Hz or more, and is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its right side by 6 dBm/Hz or more.
 6. The method for detecting RFI according to claim 1, further comprising: closing partial or all sub-carriers at the acquired frequency corresponding to the sub-carrier having RFI according to the frequency.
 7. A detecting device, comprising an acquiring unit, a detecting unit, a counting unit, and a determining unit, wherein the acquiring unit is configured to acquire parameters of at least two pairs of digital subscriber lines (DSLs); the detecting unit is configured to detect sub-carriers having RFI in each pair of the at least two pairs of DSLs according to the parameters; the counting unit is configured to count the number of line pairs having RFI on the same sub-carrier; and the determining unit is configured to determine whether the number of line pairs counted by the counting unit is greater than a preset threshold, or whether a ratio of the number of line pairs counted by the counting unit to the number of line pairs of the at least two pairs of DSLs is greater than a preset threshold, and if the number of line pairs counted by the counting unit is greater than a preset threshold or the ratio of the number of line pairs counted by the counting unit to the number of line pairs of the at least two pairs of DSLs is greater than a preset threshold, determine that RFI exists at a frequency corresponding to the sub-carrier.
 8. The detecting device according to claim 7, further comprising a configuring unit, configured to close partial or all sub-carriers at a frequency corresponding to the sub-carrier having RFI obtained by the determining unit according to the frequency.
 9. The detecting device according to claim 7, wherein the detecting unit comprises a first detecting unit, and/or a second detecting unit, and/or a third detecting unit, the first detecting unit is configured to detect that a first sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a bit number of the first sub-carrier is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its left side by 2 bits or more, and is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its right side by 2 bits or more when the parameter is the bit number of a line pair; the second detecting unit is configured detect that a second sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a signal-to-noise ratio of the second sub-carrier is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its left side by 6 dB or more, and is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its right side by 6 dB or more when the parameter is the signal-to-noise ratio of the line pair; and the third detecting unit is configured to detect that a third sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a noise power spectral density of the third sub-carrier is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its left side by 6 dBm/Hz or more, and is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its right side by 6 dBm/Hz or more when the parameter is the noise power spectral density of the line pair.
 10. A digital subscriber line (DSL) system, comprising a first device and a second device, the first device includes an acquiring unit, a detecting unit, a counting unit, and a determining unit, wherein the acquiring unit is configured to acquire parameters of at least two pairs of digital subscriber lines from the second device; the detecting unit is configured to detect sub-carriers having RFI in each pair of the at least two pairs of DSLs according to the parameters; the counting unit is configured to count the number of line pairs having RFI on the same sub-carrier in the DSLs; and the determining unit is configured to determine whether the number of line pairs counted by the counting unit is greater than a preset threshold, or whether a ratio of the number of line pairs counted by the counting unit to the number of line pairs of the at least two pairs of DSLs is greater than a preset threshold, and if the number of line pairs counted by the counting unit is greater than a preset threshold or the ratio of the number of line pairs counted by the counting unit to the number of line pairs of the at least two pairs of DSLs is greater than a preset threshold, determine that RFI exists at a frequency corresponding to the sub-carrier.
 11. The DSL system according to claim 10, wherein the detecting unit comprises a first detecting unit, and/or a second detecting unit, and/or a third detecting unit, the first detecting unit is configured to detect that a first sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a bit number of the first sub-carrier is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its left side by 2 bits or more, and is less than a maximum bit number among the bit numbers of more than three adjacent sub-carriers on its right side by 2 bits or more when the parameter is the bit number of a line pair; the second detecting unit is configured to detect that a second sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a signal-to-noise ratio of the second sub-carrier is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its left side by 6 dB or more, and is less than a maximum ratio among the signal-to-noise ratios of more than three adjacent sub-carriers on its right side by 6 dB or more when the parameter is the signal-to-noise ratio of the line pair; and the third detecting unit is configured to detect that a third sub-carrier of each pair of the at least two pairs of DSLs is the sub-carrier having RFI if a noise power spectral density of the third sub-carrier is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its left side by 6 dBm/Hz or more, and is less than a maximum density among the noise power spectral densities of more than three adjacent sub-carriers on its right side by 6 dBm/Hz or more when the parameter is the noise power spectral density of the line pair.
 12. The DSL system according to claim 10, wherein the first device further comprises a configuring unit, configured to decide to close partial or all sub-carriers at a frequency corresponding to the sub-carrier having RFI obtained from the determining unit according to the RFI frequency, and transmit information of the partial or all sub-carriers to the second device.
 13. The DSL system according to claim 12, wherein the second device is further configured to close the partial or all sub-carriers according to the information of the partial or all sub-carriers transmitted by the first device. 